Metering valves are well known from the state of the art, in particular for dispensing fluids in liquid or powder form. The fluid is generally associated with a propellant gas, and actuating the valve makes it possible to dispense a metered quantity or “dose” of fluid by means of said propellant gas. A metering valve generally includes a valve body defining a metering chamber, the valve member sliding in said metering chamber between a rest position and a dispensing position. When the valve member is in the rest position, said valve member is not connected to the inside of the metering chamber, and the metering chamber is connected to the reservoir so that it can be filled, generally by gravity, with the fluid and with the propellant gas, so as to define the dose of fluid to be dispensed the next time the valve is actuated. When the valve is actuated, the valve member is pushed into the valve body, and the passageway between the metering chamber and the reservoir is closed. Then, when the valve member reaches the vicinity of its dispensing position, the metering chamber is connected to the dispensing orifice of the valve member, thereby enabling the dose of fluid contained in the metering chamber to be discharged through the dispensing orifice of the valve member. When the user ceases to press on the valve member, said valve member is returned automatically to its rest position by a return spring, and, during this operation, the metering chamber fills again with the fluid and with the propellant gas, generally by gravity when the valve is a valve used in the upside down position, i.e. with the metering valve under the reservoir. In known metering valves, the metering chamber is thus at the same pressure as the reservoir when the valve is in the rest position because said chamber is connected directly to said reservoir. This implies high stresses on the gaskets provided at the metering chamber, and risks causing fluid to return towards the reservoir during storage, when the valve is stored in the upright position. In order to avoid such fluid return from the metering chamber to the reservoir while the valve is being stored in the upright position, and thus in order to avoid reducing the next dose, the valve member is generally provided with internal channels of complex shapes, e.g. siphon shaped, but because of the pressure existing in the metering chamber, sustaining the full dose, and therefore metering accuracy are not absolutely guaranteed.
In addition, in known metering valves, the return spring of the valve member is disposed in the body of the valve, and generally at the passageway connecting the metering chamber to the reservoir. The spring is thus in contact with the fluid and with the propellant gas. Depending on the material of the spring (generally metal) and on the type of the fluid, this can degrade said fluid.